Control apparatus



March 8, 1966 0, sc ucK 3,239,027

CONTROL APPARATUS Filed Dec. 26, 1963 2 Sheets-Sheet l FIG. 2

INVENTOR. OSCAR H. SCHUCK ATTOR NEY.

NVEN'TOR.

o. H. SCHUCK 3,239,027

CONTROL APPARATUS 2 Sheets-Sheet 2 OSCARI H. SCHUCK BY? ATTORNEY March 8, 1966 v Filed Dec. 26, 1963 7 $6 k he 2 United States Patent 3,239,027 CONTROL APPARATUS Oscar Hugo Schuck, Minneapolis, Minn., assignor to Honeywell Inc., a corporation of Delaware Filed Dec. 26, 1963, Ser. No. 339,054 15 Claims. (Cl. 181-.5)

This application is a continuation in part of application Ser. No. 201,188, filed June 8, 1962, now abandoned.

This invention pertains to acoustic devices and more particularly to acoustical devices operable to propagate acoustical energy having a particular harmonic content at a desired frequency.

There is an ever increasing need for acoustic devices Capable of generating or propagating such acoustical energy. One application for acoustical devices generating acoustical energy at a desired frequency is in fog precipitation or fog dispersion as disclosed in Patent 1,980,171, E. D. Amy, Nov. 13, 1934, and Patent 2,414,495, A. Bang, Jan. 21, 1947. Other applications include acoustical testing apparatus and under water signalling apparatus. Applications for acoustical devices generating acoustical energy having a particular harmonic content include Warning or musical tone generation (for example, a pipe organ).

The applicant has provided a unique acoustic device which comprises a frequency controlling means in combination with a fluid amplifier means and resonator means to obtain a high energy acoustical output at a desired frequency with heretofore uno'btainable efliciency. This acoustical device may also be utilized with suitable resonator design or suitable fluid amplifier design to control the harmonic content of the acoustical output.

It is therefore an object of this invention to provide an improved control apparatus. This and other objects of this invention will become apparent from a study of the accompanying specification and claims in conjunction with the drawing in which:

FIGURE 1 is a schematic representation of the applicants unique acoustical device utilizing electro-mechanical frequency control;

FIGURE 2 is a schematic representation of the applicants unique acoustical device utilizing all-fluid frequency control;

FIGURE 3 is a schematic representation of a fluid amplifier operable to produce an output signal having a particular harmonic content; and

FIGURE 4 is a schematic representation of another fluid amplifier operable to produce an output signal having a particular harmonic content.

Referring now to- FIGURE 1, reference numeral generally depicts the applicants unique acoustical device. A frequency control means 11 comprises an electromechanical driving means 12 for transforming electrical energy into mechanical energy. The electromechanical driving means 12 illustrated in FIGURE 1 is an electromagnetic type generally referred -to by those skilled in the art as a quadrupole system. Other suitable electromechanical driving means, such as a piezoelectric transducer, are within the scope of this invention. A first electro-magnet 13 and a second electromagnet 14 are provided. Electromagnets 13 and 14 are adapted to be energized from a suitable alternating current supply (not shown) by means of terminals 15 and 16. A permanent magnet armature means 17 having a north pole N and a south pole S is positioned intermediate the pole pieces of electromagnets 13 and 14. Armature means 17 is pivotally mounted at its midpoint by means of pivot 18. A link member 19 is attached to armature means 17 at one end and attached to a flapper valve 20 at the other end. Thus, movements of armature means 17 are transmitted to flapper valve 20 by link member 19. Flapper valve 20 comprises a flapper element 21, a fluid supply duct 22 which is adapted to be connected to a suitable fluid source (not shown), a first outlet duct 23, and a second outlet duct 24. Movement of flapper element 21 results in fluid being supplied to either outlet duct 23 or outlet duct 24. The fluid flows in outlet duct 23 and does not flow in outlet duct 24 when flapper element 21 is in the position illustrated in FIGURE 1. When flapper element 21 is displaced by armature 17, fluid flows in outlet duct 24 and does not flow in outlet duct 23. Thus, frequency control means 11 is operable to receive an alternating current input signal and produce a push-pull pulsating or alternate fluid flow output signal.

It should be pointed out that the applicant does not wish to be limited to frequency control means 11 schematically illustrated in FIGURE 1; other frequency control means are within the scope of the invention.

Reference numeral 30 identifies a first amplifier means. Fluid amplifier means 30 comprises a fluid supply conduit 31, a fluid chamber 32, a first control conduit 33, a second control conduit 34, a first outlet conduit 35 and a second outlet conduit 36. Supply conduit 31, control conduits 33 and 34, and outlet conduits 35 and 36 are all in communication with fluid chamber 32. It should be noted that fluid supply conduit 22 of flapper valve 20 and fluid supply conduit 31 of fluid amplifier 30 may be connected to the same fluid source. It is clear that movement of armature 17 of flapper valve 20 results in fluid fiow within either fluid control conduit 33 or 34.

A second fluid amplifier means 40 is connected to or cascaded with fluid amplifier means 30. Fluid amplifier means 40 comprises a fluid supply passage 41, a fluid chamber 42, a first control passage 43, a second control passage 44, a first outlet passage 45, and a second outlet passage 46. Supply passage 41, control passages 43 and 44, and outlet passages 45 and 46 are all in communication with fluid chamber 42. Control passage 43 is in communication with output conduit 35 of fluid amplifier 30. Control passage 44 is in communication with output conduit 36 of fluid amplifier 30.

A resonator means 50 is coupled to the outlet passages 45 and 46 of fluid amplifier 40. Resonator means 50 comprises a resonator structure 51 and a fluid medium 52. Resinator structure 51 is schematically illustrated in FIG- URE 1 as a closed end tube. Air is the fluid medium 52 utilized in FIGURE 1; however, any fluid may be utilized, liquid or gaseous.

In operation, an energization signal, for example, an alternating current at a desired frequency, is applied across terminals 15 and 16 of frequency control means 11. This results in electromagnetic driving means 12 driving armature 17 at a particular frequency. Armature 17 actually oscillates about pivot point 18. Consequently, link member 19 oscillates flapper element 21 of flapper valve 20 thereby alternatingopening outlet ducts 23 and 24 to fluid supply passage 22. Steady fluid flows in supply passage 22 is converted into alternate fluid flows within outlet ducts 23 and 24. The fluid flows within outlet ducts 23 and 24 alternate at the desired frequency.

A fluid under pressure is supplied to conduit 31 and flows into fluid chamber 32 and into outlet conduits 35 and 36. In the absence of any control signal, fluid from supply conduit 31 flows through fluid chamber 32 and into outlet conduits 35 and 36. Approximately one-half of the fluid flow enters outlet conduit 35 and the other half of the fluid flow enters conduit 36. When frequency control means 11 generates fluid flow within outlet duct 24 and consequently into control conduit 34, the fluid flowing within conduit 34 impinges upon the fluid flowing through chamber 32 into outlet conduits 35 and 36 and deflects substantially all of the fluid flowing through chamber 32 into outlet conduit 35. When frequency control means 11 generates fluid flow within outlet duct 23 and consequently within control conduit 33, the fluid flowing through chamber 32 is deflected into outlet conduit 36 in an obvious manner. Since the relatively low energy level fluid flow with control conduits 3-3 and 3 3 controls fluid flowing through chamber 32 at a higher energy level, fluid amplifier performs an amplification function.

Fluid amplifier 40 operates analogously to fluid amplifier 30; however, a higher energy output is obtained therefrom due to the amplification inherent therein. In the absence of any control signal, fluid from supply passage 41 flows through chamber 42 and into outlet passages 45 and 46. Approximately one-half the fluid flow enters outlet passage 45 and the other half of the fluid flow enters outlet passage 46. When frequency control means 11 generates fluid flow within outlet duct 24 fluid flow results in outlet conduit as explained above and consequently within control passage Fluid flow within passage 43 impinges on the fluid flowing through chamber 42 and deflects substantially all of the fluid flow into outlet passage 46. Fluid flow Within control passage 41 deflects the fluid flow into outlet passage 45 in an obvious manner. It should be noted that although two stages of amplification have been illustrated in FIGURE 1 (fluid amplifiers 3t) and a single stage of amplification or more than two stages of amplification are within the scope of the applicants invention.

In the embodiment shown in FIGURE 1, fluid flowing alternately within outlet passages and 46 is coupled with fluid medium 52 so as to generate compressional wave energy at a desired frequency. The resonator structure functions to provide impedance matching to an external medium in which acoustical energy is to propagate. The impedance matching is effective to obtain a maximum coupling efficiency at a particular frequency. More specifically, the compression wave generated within fluid medium 52 as a result of fluid flow within outlet passage 45 will be reflected from the closed end of resonator structure 51 and travel back toward the open end of resonator structure 51. As the compression wave reflected from the closed end of tube 51 reaches the outlet passage 46, it is reinforced by fluid flowing in outlet passage 46. Thus, fluid flowing in outlet passages 45 and 46 coacts with resonator means so as to obtain a high energy acoustical energy output having a given frequency. Maximum efficiency will be achieved when the flow from outlet passages 45 and 46 is introduced into the resonator at an anti-node position for the frequency used. For the simple open-ended resonator shown, one such anti-node is located at one-third of the height from the closed end, and the frequency for maximum efficiency would be that for which the length of the resonator is three-quarters of a Wave length.

An alternate embodiment of the applicants invention I is disclosed in FIGURE 2. Reference numeral 70 generally depicts the applicants unique acoustical device. Reference numeral 71 generally depicts an all-fluid frequency control means. Frequency control means 71 comprises a fluid oscillator such as disclosed in Patent 3,016,066, R. W. Warren, Jan. 9, 1962. Fluid oscillator 71 comprises a fluid supply duct 72, a fluid chamber 73, a first outlet duct 74, a second outlet conduit 75, and a feedback passage '76. Fluid supply passage 72, feedback passage 76, first outlet duct 74, and second outlet duct 75 are in communication with fluid chamber 73. Feedback conduit 76 comprises a first orifice 76 in communication with one side of chamber 73, a second orifice '76 in communication with the other side of chamber 73, and a passage 86. Supply passage 81, control passages 83 and 84, and outlet passages 85 and 86 are in communication with fluid chamber 82. Fluid control passage 83 is in communication with outlet duct 74. Control passage 84 is in communication with outlet duct 75.

First outlet passage 85 and second outlet passage 86 are in communication with a resonator means 90. Resonator means 90 comprises a resonator structure 91 and a fluid medium 92. Air is the fluid medium illustrated in FIGURE 2, however, any suitable fluid may be utilized, liquid or gaseous.

In operation, a fluid flows from fluid supply passage 72 into chamber 73 and into outlet ducts 74 and 75. The fluid flow at the entrance to outlet ducts 74 and 75 is slightly turbulent so a greater amount of fluid flows into one outlet duct, for example 74, than into the other outlet duct. When more fluid flows into outlet duct 74 than into outlet duct 75, the fluid is closer to the outer wall '77 than outer wall 78. This results in a boundary layer effect, which is well known by those skilled in the art, causing the fluid flow to lock on to the wall 77 and substantially all of the fluid then flows into duct 74. Since more fluid is flowing across orifice 76 the fluid is evacuated from orifice 76' of feedback conduit 76 more efficiently than from orifice 76" so that a pressure wave will be generated from orifice 76 to orifice 76' at the speed of sound in the local medium. Similarly, a rarefaction Wave will travel from orifice 76 to orifice 76" reducing the pressure differential across the fluid flow which tends to force the fluid flow toward orifice 74. The rarefaction wave arrives at orifice 76' at the same time the pressure wave arrives at orifice 76" and the combined effect is to shift the fluid flow from outlet duct 74 to outlet duct 75. Again a pressure and a rarefaction wave are created and cause the fluid flow to switch back to outlet duct 74. Thus, oscillator 71 produces alternate fluid flow within outlet ducts 74 and 75. The frequency of the oscillation between outlet ducts 74 and 75 depend primarily upon the length and size of the feedback passage 76 and also on the relative sizes of the orifices 76' and 76". Increasing the orifice area increases the rate of oscillation. Consequently, the frequency of the fluid oscillator is adjusted to the desired frequency by varying the length or other dimensions of the feedback path.

The alternate fluid flows within outlet ducts 74 and 75 are communicated to control passages 83 and 84 respectively. The fluid flow from fluid supply passage 81 is directed alternately into passages 85 and 86 in a manner hereinbefore explained with reference to FIGURE 1. The fluid flow within outlet passages 85 and 86 coacts with the fluid medium 92 so as to produce compressional waves at a desired frequency. The geometric configuration of the resonator structure 91 functions to increase the efliciency of coupling at the oscillation frequency. It may also be designed so as to direct or steer the compressional waves in a desired direction.

Another aspect of the applicants unique acoustical device is that it may be utilized to achieve a desired harmonic content.

The applicants unique acoustical device may be utilized to achieve a desired harmonic content for a given excitation frequency by proper design of the resonator or proper design of the fluid amplifier or both. It should be understood that continuously excited musical instruments generally produce a tone comprised of the fundamental frequency and its harmonics. The particular tone quality obtained is a function of the magnitude of the fundamental frequency and the magnitude of each of the harmonics which are present. By controlling the magnitude of the fundamental frequency and its harmonics, a particular harmonic content or tone is obtained.

With reference to the applicants unique acoustical device illustrated in FIGURES 1 and 2, the output of the frequency control means and fluid amplifier means is a square wave output having a particular excitation frequency. A closed end, uniform bore type of resonator, such as resonator 50, has not just one resonant frequency, but a series of them which are odd multiples of the fundamental mode resonance frequency. If V is the velocity of sound in the fluid utilized and L is the length of the closed tube resonator, the frequencies f of the possible simple harmonic vibrations are:

Therefore, the possible frequencies of the closed tube are the odd harmonics of the fundamental, the first overtone being the third harmonic. Now if fluid amplifier 40 furnishes a square wave signal to resonator 50, the signal contains the odd harmonics of the fundamental excitation frequency of the frequency control means 11. If one of these harmonics is also a resonant frequency of the resonator means 50', it will be prominant in the output of the resonator. A resonator means which is a M 4 resonator will have exactly the same resonance as the excitation harmonics and will, consequently, have an output similar in spectral content to the excitation. Stated otherwise, coupling this square wave signal to a closedopen resonator at its open end efficiently couples all of the odd harmonics of the excitation (fundamental) frequency to the medium. The even harmonics of the excitation (fundamental) frequency are not efficiently coupled to the medium by a closed-open resonator. The utilization of various resonator design techniques to emphasize or de-emphasize a particular harmonic is. well known to those skilled in the art, for example, the utilization of side branches, coupled cavities, and the like. That is to say, design of the resonator is effective to control the magnitude of the fundamental frequency and the harmonics in the medium to produce the desired harmonic content.

It is also possible to control the harmonic content of the resonator output by controlling the signal supplied to the resonator by the fluid amplifier means. This is accomplished by filtering (reducing) or strengthening the various harmonics so as to obtain the desired harmonic output.

A fluid amplifier means capable of controlling the harmonic content of its output signal is illustrated in FIGURE 3 and identified by reference numeral 100. Fluid amplifier means 100 comprises a fluid supply passage 101, a fluid chamber 102, a first control pas-sage 103, a second control passage 104, a first outlet passage 105, and a second outet passage 106 Supply passage 101, control passages 103 and 104, and outlet passage-s 105 and 106 are all in fluid communication with fluid chamber 102. The exhaust ends of outlet passages 105 and 106 are in communication with a resonator 110. Fluid amplifier means 100 also includes a pair of filter passages 107, 108 connected between first outlet pas-sage 105 and second outlet passage 106. The length of filter passages 107 and 108 is critical and is determined by the relationship L=V/f where L is the length of the filter passage, V is velocity of sound in the fluid to be utilized, and f is the frequency of the harmonic to be filtered or substantially reduced. Thus, a filter passage will have a length equal to the wave length of the fluid at the particular frequency of the harmonic of the excitation frequency that is to be reduced. More specifically, if resonator 110 is a closed-open resonator having a length equal to 9.2 feet, its resonance frequencies will be 30, 90, 150, 210, 270, etc. If such a resonator is excited with a 90 cycles per second square wave from the fluid amplifier which contains 90, 270, 450, etc. harmonics, the resonator will have an output rich in these harmonics. If a different harmonic content is desired, the square wave signal from the fluid amplifier is modified by providing filter passages therein. For example, to reduce the 270 cycles per second harmonic the outlet passages 105, 106 of fluid amplifier are connected by a filter passage, such as 108, having a length equal to the wavelength A at that frequency. If the fluid utilized is air, the length of filter passage 108 would be:

V 1100 L 270 4.08 feet In a similar manner the length of a filter passage to reduce the 450 cycles per second harmonic, such as 107, would be 2.44 feet. Thus, the 270 and 450 cycle per second harmonics are substantially reduced or filtered from the amplifier signal. Accordingly, the resonator output is substantially without these harmonics and the desired harmonic content is obtained.

It is possible to strengthen the odd harmonics in the excitation frequency by decreasing the length of the excitation pulsesv This can be accomplished by providing a fluid amplifier as illustrated in FIGURE 4. Fluid amplifier means comprises a fluid supply passage 121, a fluid chamber 122, a first control passage 123, a second control passage 124, a first outlet passage 125, a second outlet passage 126, and a third outlet passage 127. Supply passage 121, control passages 123 and 124, and outlet passages 125, 126, and 127 are all in communication with fluid chamber 122. Outlet passages 125 and 127 are coupled to a resonator means 128. Outlet passage 126 is in communication with a suitable mufiler or fluid return passage (not shown). Amplifier 120 functions to provide excitation pulses or signals of relatively short length or duration to the resonator means 128. This is because, by proper choice of the relative sizes of the three outlet passages, the duration of the outlet pulses can be made significantly less than one-half cycle. Fluid flow during the part of the half cycles in which outlet passages 125 and 127 are not carrying flow is dumped into outlet passage 126 and has no effect on resonator 128. Since decreasing the length of the excitation pulses strengthens the odd harmonics of the excitation frequency, some control over the final harmonic content in the medium is achievable.

It is clear that it is possible to control the harmonic content of the resonator output by controlling the signal supplied to the resonator by the fluid amplifier. Thus, it is possible to control the harmonic content of the output signal by either suitable fluid amplifier design or suitable resonator design or both.

A specific example of providing a desired harmonic content is utilizing the applicants unique acoustical device to produce a desired pipe organ tone. The excitation frequency is controlled .-by the frequency control means which produces acoustical signals at low energy level. The fluid amplifier means amplifies the acoustical signals to achieve the desired resonator excitation level and to provide a signal with the desired harmonic content. The output of the fluid amplifier means is coupled to an organ pipe-like resonator of a particular rank which is designed to produce a particular harmonic content desired. The application of the applicants invention to a pipe organ provides an acoustic output having true pipe organ tone with perfectly stable tuning.

While I have shown and described the specific embodiments of this invention, further modification and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown, and I intend in the appended claims to cover all modifications which do not depart from the spirit of the scope of this invention.

I claim as my invention:

1. An acoustic device comprising:

frequency control means, said frequency control means including a fluid oscillator having a fluid supply duct, a first fluid chamber, a feedback passage, and first and second outlet ducts, said supply duct, said feedback passage and said first and second outlet ducts being in communication with said first fluid chamber;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a second fluid chamber, first and second control passages, and first and second outlet passages, said supply passage, said first and second control passages, and said first and second outlet passages being in communication with said fluid chamber, said first and second outlet ducts being in communication with said first and second control passages respectively;

and resonator means, said resonator means including a resonator structure and a fluid medium, said first and said second outlet passages communicating with said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second ducts and Within said first and second control passages, fluid flow within said first control passage resulting in fluid flow within said first outlet passages, fluid flow Within said second control passage resulting in fluid flow within said second outlet passage, said fluid flow within said output passages coacting with said resonator means so as to propagate compressional wave energy at a desired frequency.

2. An acoustic device comprising:

frequency control means, said frequency control means including a fluid supply duct, an electrically energized flapper valve, and first and second outlet ducts;

fluid amplifier means, said fluid amplifier means including a fluid supply conduit, a fluid chamber, first and second amplifier control conduits, and first and second amplifier outlet conduits, said supply conduit, said first and second amplifier control conduits, and said amplifier outlet conduits being in communication with said fluid chamber, said first and second outlet ducts being in communication with said first and second amplifier control conduits respectively;

and resonator means, said resonator means including a resonator structure and a fluid medium;

said first and said second amplifier outlet conduits communicating with said resonator means, said frequency control means operable to provide alternate fluid flow Within said first and said second outlet ducts and within said first and second amplifier control conduits, fluid flow within said first amplifier control conduit resulting in fluid flow Within said first amplifier outlet conduit, fluid flow within said second amplifier control conduit resulting in fluid flow within said second amplifier outlet conduit, fluid flow within said first and second amplifier outlet conduits coacting with said resonator means so as to generate compressional wave energy at a desired frequency.

3. An acoustic device comprising:

electromechanical frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first and second outlet passages, said supply passage, said first and second control passages, and said outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and second control passages;

and resonator means, said resonator means including a resonator structure and a fluid medium;

said first and said second outlet passages communicating with said resonator means, said frequency control means operable to provide alternate fluid flow within said first and second control passages, fluid flow within said first control passage resulting in fluid flow Within said first outlet passage, fluid flow within said second control passage resulting in fluid flow within said second outlet passage, fluid flow within said outlet passages coacting with said resonator structure and said fluid medium so as to propagate compressional wave energy at a desired frequency.

4. An acoustic device comprising:

frequency control means, said frequency control means including a fluid supply passage, an electrically energized flapper valve, and first and second outlet ducts;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first and second outlet passages, said supply passages, said first and second control passages, and said first and second outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and second control passages;

and resonator means, said resonator means including a resonator structure and a fluid medium;

and said second outlet passages communicating with said resonator means, said frequency control means, said fluid amplifier and said resonator coacting so as to generate compressional wave energy at a desired frequency.

5. An acoustic device comprising:

frequency control means;

said frequency control means including fluid oscillator means having first and second outlet ducts;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, first and second control passages, and first and second outlet passages, said first and second control passages being in communication with said first and said second outlet ducts;

and resonator means, said first and said second outlet passages coupled to said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second control passages, fluid flow within said first control passage resulting in fluid flow in said first outlet passage, fluid flow within said second control passage resulting in fluid floW in said second outlet passage, fluid flow within said outlet passages coacting with said resonator so as to propagate compression wave energy at a desired frequency.

6. An acoustic device comprising:

frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first and second outlet passages;

said supply passage, said first and said second control passages, and said first and second outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and said second control passages;

and resonator means, said first and said second outlet passages coupled to said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second outlet passages, fluid flow within said first and said second outlet passages coacting with said resonator so as to generate compressional wave energy at a desired frequency and control the harmonic content thereof.

7. A tone generator comprising:

frequency control means;

fluid amplifier means, said frequency control means being connected to said fluid amplifier means;

and resonator means, said resonator means being coupled to said fluid amplifier, and said frequency control means, said fluid amplifier and said resonator coacting so as to generate compressional wave energy and control the harmonic content thereof.

8. An acoustic device comprising:

frequency control means;

fluid amplifier means, said frequency control means being connected to said fluid amplifier means;

and resonator means, said resonator means being coupled to said fluid amplifier, and said frequency control means, said fluid amplifier and said resonator coacting so as to propagate compressional wave energy at a desired frequency.

9. An acoustic device comprising:

electromechanical frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, first and second outlet passages, and a filter passage connected between said first and said second outlet passages, said filter passage having a length equal to the velocity of sound in the fluid utilized in said fluid amplifier means divided by the frequency of the harmonic to be filtered, said supply passage, said first and second control passages, and said first and said second outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and second control passages;

and resonator means, said resonator means icluding a resonator structure and a fluid medium;

said first and said second outlet passages communicating with said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second control passages, fluid flow within said first control passage resulting in fluid flow within said first outlet passage, fluid flow within said second control passage resulting in fluid flow Within said second outlet passage, said filter passage being effective to substantially reduce said harmonic so as to provide a signal in said outlet passages of said fluid amplifier of a desired harmonic content, said signal within said outlet passages coacting with said resonator structure and said fluid medium so as to generate compressional wave energy having a desired frequency and harmonic content.

10. An acoustic device comprising:

frequency control means;

said frequency control means including fluid oscillator means having first and second outlet ducts;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, first and second control passages, first and second outlet passages, and a filter passage connected between said first and said second outlet passages, said filter passage having a length equal to the velocity of sound in the fluid to be utilized in said fluid amplifier means divided by the frequency of the harmonic to be filtered, said first and second control passages being in communication with said first and second outlet ducts;

and resonator means, said first and said second outlet passages coupled to said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second control passages, fluid flow within said first control passage resulting in fluid flow in said first outlet passage, fluid flow within said second control passage resulting in fluid flow in said second outlet passage, said filter passage being operable to substantially reduce said harmonic so as to provide a signal in said outlet passages of said fluid amplifier having a desired harmonic content, said signal within said outlet passages coacting with said resonator so as to propagate compressional Wave energy having a desired frequency and harmonic content.

11. An acoustic device comprising:

frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, first and second outlet passages, and a filter passage connected between said first and said second outlet passages, said supply passage, said first and second control passage, and said first and second outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and said second control passages;

and resonator means, said first and said second outlet passages coupled to said resonator means, said frequency control means operable to provide alternate fluid flow within said first and said second control passages, said fluid amplifier means operable to provide a signal in said first and said second outlet passages having a desired harmonic content, said resonator means operable to receive said signal from said first and second outlet passages and generate compressional wave energy having a desired frequency and harmonic content.

12. An acoustic device comprising:

frequency control means, said frequency control means including first and second outlet ducts;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first, second, and third outlet passages, said supply passage, said firs-t and second control passages, and said first, second, and third outlet passages being in communication with said fluid chamber, said first and second outlet ducts being connected to said first and second control passages, said second outlet passage being connected to muffler means, said fluid amplifier being operable to provide an output signal in said first and said third outlet passages having a desired harmonic content;

and resonator means, said resonator means including a resonator structure and a fluid medium, said first and said third outlet passages communicating with said resonator means, said frequency control means, said fluid amplifier and said resonator coacting so as to generate compressional wave energy and control the harmonic content thereof.

13. An acoustic device comprising:

frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first, second, and third outlet passages, said supply passage, said first and second control passages, said first, second, and third outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and second control passages, said second outlet passage being connected to mufller means;

and resonator means, said resonator means including a resonator structure and a fluid medium, said first and said third outlet passages communicating with said resonator means, said frequency control means, said fluid amplifier and said resonator coacting so as to generate compressional wave energy and control the harmonic content thereof.

14. An acoustic device comprising:

frequency control means;

fluid amplifier means, said fluid amplifier means including a fluid supply passage, a fluid chamber, first and second control passages, and first and second outlet passages, and a plurality of filter passages connected between a said first and said second outlet passages;

said supply passage, said first and second control pas sages, and said first and second outlet passages being in communication with said fluid chamber, said frequency control means being connected to said first and said second control passages;

and resonator means, said first and said second outlet passages coupled to said resonator means, and said frequency control means, said fluid amplifier means, and said resonator means coacting so as to generate compressional wave energy and control the harmonic content thereof.

15. A tone generator comprising:

frequency con-trol means;

1 1 12 fiuid amplifier means, said fluid amplifier means being coacting so as to generate compressional wave enadapted to provide an output signal having a desired ergy and control the harmonic content thereof.-

harmonic content, said frequency control means be ing connected to said fluid amplifier means; and resonator means, said resonator means being cou- 5 BENJAMIN BORCHELT Primary Examiner pled to said fluid amplifier, and said frequency control means, said fluid amplifier and said resonator GLANZMAN Assistant Exammer' No references cited. 

8. AN ACOUSTIC DEVICE COMPRISING: FREQUENCY CONTROL MEANS; FLUID AMPLIFIER MEANS, SAID FREQUENCY CONTROL MEANS BEING CONNECTED TO SAID FLUID AMPLIFIER MEANS; AND RESONATOR MEANS, SAID RESONATOR MEANS BEING COUPLED TO SAID FLUID AMPLIFIER, AND SAID FREQUENCY CONTROL MEANS, SAID FLUID AMPLIFIER AND SAID RESONATOR COACTING SO AS TO PROPAGATE COMPRESSIONAL WAVE ENERGY AT A DESIRED FREQUENCY. 